1. Field of the Invention
The present invention relates to control of cooling means placed inside an image formation apparatus proper.
2. Related Background Art
A cooling fan is placed in the proximity of an image heating and fixing apparatus mounted on an image formation apparatus such as an electrophotographic copying machine or a printer to prevent temperature rise inside the apparatus proper due to heat of the fixing apparatus. The cooling fan efficiently exhausts hot air generated by the fixing apparatus to the outside of the main body of the image forming apparatus so as to prevent an adverse thermal effect on image formation by keeping heated air from flowing into a so-called image formation portion.
As for such an image formation apparatus, efforts have been made to design it in a form in which there are minimum gaps among components and devices in order to meet miniaturization needs. As a result thereof, there are many cases where other components and devices such as a transfer belt and a developing device must be placed in the proximity of the fixing apparatus which is a heating element.
Concerning such an image formation apparatus, to prevent a problem that the heat generated by the fixing apparatus has an adverse effect on surrounding components, there is a technique which has been very commonly employed, wherein the cooling fan is usually provided inside the image formation apparatus and the hot air generated by the fixing apparatus is efficiently exhausted to the outside of the main body of the image forming apparatus so as to prevent the adverse thermal effect on each portion.
In the case of the image formation apparatus having such a configuration, a control temperature of the fixing apparatus when the main body of the apparatus is on standby is different from that during actual printing operation. And there are many cases where the former temperature is set lower than the latter.
In conjunction with this, control is exerted to switch a rotation number (rotational speed) of the cooling fan provided inside the main body of the apparatus to have different speeds between on standby and during the actual printing operation of the main body of the apparatus. In general, it is often controlled to be at a slower rotation number on standby than during the actual printing operation.
In the case where an error including a sheet jam occurs during the printing in the image formation apparatus, it is common that the actual printing operation thereof is stopped in emergency, energization to a heater of the fixing apparatus is turned off, and the rotation number of the cooling fan is switched to the same rotation number as that on standby (Japanese Patent Application Laid-Open No. 2000-007205 and Japanese Patent Application Laid-Open No. 2001-005366 for instance).
Jam handling is performed by opening a release door of the image formation apparatus and opening the inside thereof (Japanese Patent Application Laid-Open No. 11-190924 for instance). A power circuit is automatically cut off by opening the release door so as to secure electrical safety of a user performing the jam handling. Therefore, as described above, driving of the cooling fan switched to the same rotation number as that on standby also stops on cutting off the power circuit by opening the release door.
The following problem arises, however, in the case of thus keeping the rotation number of the cooling fan in all error statuses constant.
For instance, in the case where a sheet stays in the proximity of the fixing apparatus and causes a jam, the energization to the heater of the fixing apparatus is off but the temperature of the fixing apparatus is still high when the user handles the jam. For that reason, it is not easy to handle it due to the heat diffused from the fixing apparatus. Therefore, it is desirable to cool this portion as efficiently as possible during the time from stopping the operation of the image formation apparatus in emergency due to jam detection until having the power circuit cut off by opening the release door for the jam handling. And it is desirable to rotate the fans placed in the proximity of the fixing apparatus, for instance, at a faster speed than usual during the time.
In the case where the sheet stays at a location other than the proximity of the fixing apparatus and causes the jam, however, there is a problem that, if the same fan control as previously described is performed, the fixing apparatus itself is quenched, and if the user tries to restart the printing operation after performing the jam handling, it takes time for the fixing apparatus once cooled to reach a target control temperature, leading to a complaint of extended wait time.
Even in the case of the jam in the proximity of the fixing apparatus likewise, a desirable cooling speed may be different between the case of a regular sheet and the case of an OHT film.
For instance, there is a problem that, if a certain type of OHT film causes the jam in the proximity of the fixing apparatus and is left at a high temperature, it drastically gets soft and deformed, and hardens again in that form if left at an ordinary temperature so that the jam handling becomes very difficult.
Therefore, it is necessary, in the case of the jam with such a film, to maximize the rotation number of the cooling fan and quench it.
To be more specific, it is desirable to allow adequate control of the cooling fan according to the forms, that is, what kind of jam occurred and what kind of error occurred in the apparatus proper respectively.